This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The broad long-term objective of this project is to develop members of the Plasmodium vivax merozoite surface protein-3 (PvMSP-3 ) and PvMSP-9 recombinant proteins as candidate malaria vaccine products. This laboratory originally identified, expressed, and characterized these proteins and their potential as malaria vaccine candidates. We have identified and characterized additional members of the PvMSP3 family (total of eleven genes) and recombinant products representing each gene have been produced for biochemical characterization. The recombinant products were expressed in a prokaryotic system and have been used to produce polyclonal rabbit antisera which recognize each PvMSP3 protein. In keeping with our objective to evaluate the native immune response in humans, five recombinant products representing the PvMSP3 alpha (PvMSP-3a) protein were produced, purified and tested (Lima-Junior et al 2008). Finally, the same five products representing the PvMSP3 alpha (PvMSP-3a) protein were tested for safety, immunogenicity and efficacy in Saimiri boliviensis monkeys, and the results are currently being analyzed. These primates are susceptible to P. vivax infections and can serve very well as a direct challenge model.